Canon NP6012 Service Manual page 73

4. Controlling the Voltage Level of the
DC Bias to Suit the Copy Density
Setting
The copier varies the DC bias control
signal (DCBPWM) according to the settings
shown below to vary the DC component volt-
age, thereby controlling the copy density.
* setting of the density adjusting lever
(manual control mode)
* output of the AE sensor (automatic
control mode)
¢ setting of density correction dial
(VR107)
* type of developing assembly
DC bias: -50V to -550V
The density correction dial (VR107) on
the DC controller PCB may be used to
adjust the DC bias voltage, there by correct-
ing foggy images caused by changes in the
sensitivity of the photosensitive drum. The
density correction dial functions when the
density is adjusted in manual mode or during
automatic density adjustment mode.
Figure 3-310
See Figures 3-311 and 312 for changes
in the DC bias according to the setting of the
density adjusting lever in manual mode and
to the changes in the AE sensor output in
automatic mode.
3-28 COPYRIGHT © 1995 CANONINC.
Density of
Test Chart Newspaper original
—t - >
-100 + -
-200 + ee
-280 Sy,
-300 - ~S
Se 2319 ney (darker)
-400 - hg 2
= 40 nce
-500 ,
y "+7589 neg (lighter)
Developing
bias DC
component (V)
AE mode ON
Figure 3-311
Copy density lever
1 5 9
0 -—+ { +>
Developing
bias DC
component (V)
Manual! Density adjustment
Figure 3-312
CANON NP&O12/NPGO12F/NPS212 REV SEPT. 1995 PRINTED IN JAPAN (IMPRIME AU JAPON)